Log-in to your G Mail account.
In chat box, hover mouse over any contact and in more options you will find Send SMS:
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HOW TO SEND FREE SMS FROM GMAIL
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HOW TO SEND FREE SMS FROM GMAIL
You can now start chat. What`s even good, you get 50 free message initially, and you get 5 message credit for every reply you get.
HAVE A TRICKY DAY!!!